Pneumatic liquid disposal system

ABSTRACT

Waste liquid is discharged pneumatically into a liquid disposal system through a discharge conduit from an outlet of a vessel which receives such waste liquid. Flow control mechanism is operatively associated with the discharge conduit which controls the flow of liquid from the vessel and normally functions to maintain the liquid level in the vessel at a level above the level of the outlet. When the flow control mechanism malfunctions and the liquid falls to a level at the vicinity of the outlet and at such time the discharge conduit is in communication with the system and at a partial vacuum, a body capable of floating in the liquid is drawn by suction toward the outlet in airtight sealing relation therewith, so that flow of air from the vessel into the system will be prevented.

I Umted States Patent 1 [1 11 3,746,032

Wallgren July 17, 1973 [5 PNEUMATIC LIQUID DISPOSAL SYSTEM 3,482,267 12/1969 Liljendahl 251 5 x Invention Anton i -g 2,796,883 6/1957 Thompson137/399 Sweden Primary Examiner-Alan Cohan Assistant ExaminerGerald A.Michalsky [73] Assignee. glljltglzpllaget Electrolux, Stockholm, AtmmeyEdmund A. Fenander [22] Filed: Aug. 4, 1971 [57] ABSTRACT I [21] App!168,975 Waste liquid is discharged pneumatically into a liquid disposalsystem through a discharge conduit from an [30] Au g g Priority Data 1133 outlet of a vessel which receives such waste liquid. we en Flowcontrol mechanism is operatively associated with [52] us. Cl 7/205 4/10137/l92 the discharge conduit which controls the flow of liquid 5137/423 from the vessel and normally functions to maintain the [5 Int ClFl6k 31/18 liquid level in the vessel at a level above the level of the[58] Field 137/192 outlet. When the flow control mechanism malfunctions399 and the liquid falls to a level at the vicinity of the outlet and atsuch time the discharge conduit is in communi- [56] References Citedcation with the system and at a partial vacuum, a body capable offloating in the liquid is drawn by suction to- UNITED STATES PATENTSward the outlet in airtight sealing relation therewith, so Llljendahlflow of air from the vessel into the System be 3,224,460 12/1965 Cann137/399 prevented 1,789,706 l/1931 Kieselbach... 137/192 3,115,14812/1963 Liljendahl.... 137/205 17 Claims, 10 Drawing Figures 3,351,28111/1967 Keil 137/192 X BRING COA/OU/T ,5 CONNECTED 70 DISPOSJL SYSTEMnever/41 tact/0M UGLID N553 4M0 08B MEN sum 2 or 5 PAIENIEU JUL I 7 I975PNEUMATIC LIQUID DISPOSAL SYSTEM BACKGROUND OF THE INVENTION 1. Field ofthe Invention In pneumatic liquid disposal systems waste liquid flowsfrom sanitary conveniences through branch conduits to a longer mainconduit which is maintained at a partial vacuum. The sanitaryconveniences operatively associated with each branch line form part ofan operating unit of the liquid disposal system which includes a vesselin which waste liquid collects and from the outlet of which the liquidis discharged through a conduit into the branch line.

2. Description of the Prior Art In pneumatic liquid disposal systemsoperating at a partial vacuum flow control mechanism is provided in thedischarge conduit of each operating unit. Such flow control mechanismcontrols the flow of liquid from the outlet of the vessel of eachoperating unit to a branch line and normally functions to maintain theliquid level in the vessel at a level above the level of the outlet.

When the flow control mechanism malfunctions so that the dischargeconduit remains in communication with the branch line and the liquidlevel in the vessel falls to the level of the outlet, air in the vesselcan be drawn by suction into the discharge conduit and flow into thepneumatic liquid disposal system through the branch line. This isobjectionable because the partial vacuum developed and maintained in thesystem will be impaired and can be inadequate to propel waste liquidpneumatically into other branch lines of the system from the vessels ofother operating units in which such liquid collects.

SUMMARY OF THE INVENTION My invention relates to structure which, inaddition to the flow control mechanism normally associated with eachoperating unit of a pneumatic liquid disposal system, functions as asafety measure to prevent flow of air from a vessel of an operating unitinto the system when the flow control mechanism malfunctions and a pathof flow for such air is established from the outlet of the vesselthrough a discharge conduit into the system which is at a partialvacuum. Such additional structure functions independently of the controlmechanism and is operable to prevent air in the vessel of an operatingunit from flowing through the outlet thereof when the flow controlmechanism malfunctions and the partial vacuum in the system becomeseffective to draw such air into the system by suction from the vessel inwhich the liquid level has fallen to the level of the outlet.

accomplish this by providing safety structure which comprises a bodycapable of floating in the liquid held in a vessel of an operating unit.When a partial vacuum develops at the outlet of the vessel and theliquid in the vessel falls to the level of the outlet the floating bodyis drawn by suction toward the outlet in airtight sealing relationtherewith so that flow of air into the system will be prevented. Bypreventing flow of air into a pneumatic liquid disposal system in thismanner from the outlet of a vessel forming a part of an operating unitof the system, the partial vacuum developed and maintained in the systemto propel waste liquid therein from other operating units will not beimpaired.

BRIEF DESCRIPTION OF THE DRAWING In the drawing, FIG. 1 is a schematicrepresentation of a pneumatic liquid disposal system embodying myinvention;

FIG. 2 is an elevation view, partly in section, of flow controlstructure which is schematically represented in FIG. I and embodies theinvention to prevent flow of unwanted air into the liquid disposalsystem;

FIG. 3 is an enlarged perspective view, partly in section, of the mainpneumatically-operated valve unit shown in FIG. 2 which coacts with thecontrol valve operable responsive to liquid level;

FIG. 4 is an enlarged fragmentary sectional view of parts shown in FIG.3 to illustrate details more clearly;

FIG. 5 is an enlarged fragmentary sectional view diagrammaticallyillustrating the control valve shown in FIG. 2 operable responsive toliquid level;

FIG. 6 is an enlarged fragmentary sectional view diagrammaticallyillustrating the manually operable valve shown in FIG. 2 operativelyassociated with the flow control structure;

FIGS. 7 to 10 are fragmentary view of flow control structure like thatshown in FIG. 1 illustrating modifications of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 I have shown myinvention embodied in a pneumatic sewage or liquid disposal systemhaving one or more primary conduits or pipe lines 10 for conductingwaste liquid to a receiving tank 11 from sanitary conveniences 12, suchas bathtubs and wash basins, for example. The pneumatic sewage or liquiddisposal system is maintained under partial vacuum which may be one-halfof atmospheric pressure, for example, in any suitable manner. As seen inFIG. 1, a vacuum pump 14 is connected to the receiving tank 11.

The waste liquid from the sanitary conveniences 12 is conducted throughbranch lines or secondary conduits 15 to the primary pipe lines 10. Thesanitary conveniences 12 associated with each branch line 15 form partof an operating unit 16 of the'system which includes a vessel 17 forreceiving waste liquid and flow control mechanism 18 for controlling thedischarge of waste liquid into the branch lines 15 from the vessels 17which may be referred to as septic tanks.

As shown in FIG. 2, each operating unit 16 includes a conduit 19 throughwhich liquid flows froman outlet 20 of a sanitary convenience or place12 to an inlet 21 of the vessel 17 and a discharge conduit 22 having itsinlet end connected to an outlet 23 of the vessel 17 and its oppositedischarge end connected to a branch pipe line or conduit 15.

The flow control mechanism 18 is operatively associated with thedischarge conduit 22 which opens when the body of liquid 24 in thevessel 17 rises to the level A and closes when it falls to the level B.The flow control mechanism 18 includes a main valve 25 coupled in thedischarge conduit 22. As seen in FIG. 3, the valve 25 is embodied in asection of the discharge conduit 22 having an oval-shaped opening in thetop thereof and an inverted U-shaped bottom 26 at the region of such topopening. A ridge 26a, which is transverse to the longitudinal axis ofthe conduit 22, extends inward therefrom about the conduit between theopposing edges of the top opening.

An elastic wall 27 of the shape shown in FIG. 3 is positioned at the topopening of the conduit 22. The elastic wall 27, which maybe formed ofrubber, for example, is provided with a flange 28 which tits in anairtight manner over an outwardly bent edge 29 about the top opening inthe conduit 22. The elastic wall 27 serves as a valve member of thevalve 25 and is movable between closed and open positions to control thedischarge of waste liquid from the discharge conduit 22 into the branchpipe line or conduit 15 forming a part of the pneumatic liquid disposalsystem.

A device 30 operates the main valve 25 and moves the elastic valvemember 27 between its closed and open positions. In FIG. 3 it will beseen that the elastic valve member 27 is formed with bosses 31 and 32 inwhich lifting buttons 33 and 34 are vulcanized. The buttons 33 and 34coact with pairs of spaced horizontal bars 35 and 36 which are fixed toand project from two arms 37 and 38 of the operating device 30. The arms37 and 38 have bottom edges of semicircular form which, along theirentire lengths, can engage the elastic valve member 27 and press thelatter into sealing engagement with the bottom 26 of the conduit 22 atopposing sides of the ridge 26a, as shown in FIG. 4.

The arms 37 and 38 are formed at the periphery of a plate 39 whichdepends downward from and is fixed to the bottom 40 of an uprightcylindrical-shaped vessel 41 having a side wall 42 and in which a metalweight 43 is positioned. Another inverted U-shaped vessel 44 is disposedabove and spaced from the vessel 41.

The vessel 44 is supported in a fixed'position in any suitable manner,as by a frame 45, for example, and includes a top 46 and a side wall 47extending downward therefrom. The bottom edge of the side wall 47 ofvessel 44 and top edge of the side wall 42 of the vessel 41 areconnected by a member 48 of annular shape which is formed of a suitableresilient material like rubber, for example. The annular-shaped member48 is secured to the side walls 42 and 47 in an airtight manner.

When the operating device 30 is connected to a region at a partialvacuum in a manner that will be explained presently, the vessel 41 willmove upward with respect to vessel 44 due to the'resilient connection 48therebetween. When this occurs the plate 39 and arms 37 and 38 will bemoved upward and lift the buttons 33 and 34, thereby lifting the elasticvalve member 27 from its closed or seated position in the conduit 22.

Conversely, when the operating device 30 is connected to a region at ahigher pressure, such as atmospheric pressure, in a manner that will beexplained presently, the vessel 41, with the aid of the weight 43, willmove downward with respect to the vessel 44 due to the resilientconnection between the vessels. When this occurs the plate 39 will bemoved downward and the arms 37 and 38 will exert force against theelastic valve member 27 and move it firmly against the bottom 26 of theconduit 22 at opposing sides of the ridge 26a.

The main valve 25 and operating device 30 just described are generallylike those described in U. S. Pat. No. 3,482,267 to Sven A. J.Liljendahl, granted Dec. 9, 1969. The disclosure in the aforementionedLiljendahl patent may be considered as being incorporated in thisapplication, and, if desired, reference may be made thereto for adetailed description of the main valve 25 and operating device 30.

The operating device 30 is connected by a conduit section 50, a controlvalve 51 and a conduit 52 to a region 53 of the discharge conduit 22which is at a partial vacuum and downstream from the main valve 25. In amanner that will be described presently the operating device 30 isconnected by conduit section 50 and passageway means formed in thecontrol valve 51 to the space 54 above the liquid level in the vessel 17and will be influenced by the pressure prevailing in the latter which isat atmospheric pressure.

As seen in FIG. 5 the control valve 51 comprises a shell 55 havinghollow bosses or nipples S6, 57 and 58, the conduit sections 50 and 52being connected to the bosses 56 and 57, respectively, and the boss 58being in communication with air at atmospheric pressure in the space 54.

The bosses 56, S7 and 58 are connected by tubing 59, 59a, 59b, 60 and 61to apertured regions of a hollow sleeve 62 vertically disposed withinthe shell 55. A valve member 63 having a pair of passageways64 and 65therein is vertically movable within the sleeve 62 between upper andlower positions. The control valve 51 is open when the valve member 63is in its illustrated upper position at which time it bears against theupper closed end 66 of the hollow sleeve 62 which is formed with a ventopening 67. When the control valve 51 is open the conduit sections 50and 52 are connected to one another and the operating device 30 is incommunication with the region 53 of the discharge conduit 22 which is ata partial vacuum. This connection between the conduit sections 50 and 52includes the boss 56,

tubing 59 and 59a, passageway 64 in the valve member 63, tubing 60 andboss 57. When the connection just described is completed the elasticvalve member 27 of the main valve 25 moves to its open position, aspreviously explained.

The control valve 51 is closed when the valve member 63 moves downwardfrom its illustrated upper position in FIG. 5. When the control valve 51is closed the conduit sections 50 and 52 are disconnected from oneanother and the operating device 30 is in communication with the space54 in which air at atmospheric pressure is present. This connectionincludes the conduit section 50, boss 56, tubing 59 and 59b, passageway65 in the valve member 63, tubing 61 and boss 58.

The control valve 51 is operable responsive to the liquid level in thevessel 17 and opens when the liquid level rises to the level A andcloses when the liquid falls to the level B. As shown, the control valve51 is operatively connected to a device 66 which functions to move valvemember 63 between its upper and lower positions responsive tohydrostatic pressure of liquid in the vessel 17.

By way of example the device 66, as diagrammatically shown in FIG. 5,may comprise a hollow tube 67a which extends downward from the controlvalve 51 and is connected to the hollow sleeve 62 and at its lower endis fixed to an expansible and contractible bellows 68. A rod 69extending axially through the tube 670 is connected at its upper andlower ends to the valve member 63 and to the bottom of the bellows 68,respectively.

When the liquid in the vessel 17 reaches the level A the hydrostaticpressure of the liquid head acting on the bellows 68 is sufficient tocontract the latter and cause the valve member 63 to move to itsillustrated upper position described above, whereby the control valve 51will open and render the operating device 30 operable to open the mainvalve 25. When this occurs the partial vacuum prevailing in thedischarge conduit 22 becomes effective to suck and withdraw waste liquidfrom the vessel 17. As the liquid in the vessel 17 falls the hydrostaticpressure acting on the bellows 68 decreases whereby the latter expandsand causes the valve member 63 to move to its lower position describedabove, whereby the control valve 51 will close and the operating device30 becomes effective to close the main valve 25 in the manner previouslyexplained. When the main valve 25 now is closed the partial vacuum inthe branch conduit no longer is transmitted to the vessel 17 through thedischarge conduit 22 and the liquid in the vessel will remain at thelevel B which is above the level of the outlet 23.

Snap-acting mechanism 70 can be employed in the device 66 to effectopening of the control valve 51 when the liquid rises to the level A andclosing thereof when the liquid falls to the level B. The snap-actingmechanism may comprise a pair of levers 71 having their inner endspivotally connected at 72 to the rod 69 and their outer ends providedwith pins 720 movable in elongated slots 73 formed in lugs 74 fixed tothe side wall of the hollow sleeve 62. A coil spring 75 is connected atits ends to the pins 72a and functions to promote axial movement of therod 69 after the levers 71 pass dead center. Hence, the snap-actingmechanism 70 functions to keep control valve 51 in its closed positionuntil the force developed by the bellows 68 at the liquid level A issufficient to move the levers 71 past their dead center position atwhich time the coil spring 75 becomes effective to move rod 69 upward tocause the valve member 63 to move to the position illustrated in FIG. 5.

Conversely, the snap-acting mechanism 70 functions to keep control valve51 in its open position until the force developed by the bellows 68 atthe liquid level B is sufficient to move the levers 71 past their deadcenter position at which time the coil spring 75 becomes effective tomove the rod 69 downward to cause the valve member 63 to move to itslower position at which the passageway 65 is in communication with thetubing 59 and 59b and 60. A vent opening 76 may be provided in the wallof the tube 67 so that the interior of the device 66 will be atatmospheric pressure.

As shown in FIG. 2, the vessel 17 is provided with a coarse grating 77which is vertically disposed therein and extends upward from the bottomof the vessel to a height well above the liquid level A. The grating 70is disposed between the inlet 21 and outlet 23 of the vessel 17 so thatall waste liquid must flow therethrough.

For visually indicating the level of the liquid body 24 a float 78 isprovided in the vessel 17. A rod 79 which functions as a level indicatoris fixed to the float 78 and extends upward therefrom through anopen-ended hollow tube 80 which is fixed to the top of the vessel 17 andextends therethrough. When the liquid level in the vessel 17 becomesabnormally high the rod 79 will project above the upper end of the tube80 and indicate that the flow control mechanism is not functioningproperly.

A valve 81 is provided for manually rendering the operating device 30operable at will to open the main valve 25. As diagrammatically shown inFIG. 6, the valve 81 includes a jacket 82 which is connected in theconduit section 50 at 83 and 84. A cross connection 85 connects theconduit section 52 to the jacket 82 at 86.

A plug 87, which is rotatable within the jacket 82, is provided with anoperating handle 88 to connect conduit section 52 to the conduit section50 through the cross connection 85. The plug 87 is formed with apassageway 89 which, as shown in FIG. 6, is in such a position that theoperating device 30 will be connected to the control valve 51 and thelatter will function to control the flow control mechanism responsive tothe liquid level in the vessel 17, as explained above.

When it is desired to control the operating device 30 manually to openthe main valve 25, the plug 87 is turned clockwise 90 by the handle 88whereby the ends of the passageway 89 are in communication with theaperturedregions 84 and 86 of the jacket 82. Under these conditions thefull effect of the partial vacuum at the region 53 of the dischargeconduit 22 will be transmitted to the operating device 30 through theconduit section 52, cross connection 'and passageway 89 of the plug 87.When the plug 87 now is turned counterclockwise 90 by the handle 88 theplug will again be in the position illustrated in FIG. 6 and theoperating device 30 will function in a normal manner responsive to thelevel of the liquid in the vessel 17.

In FIG. 2 it will be seen that the vessel 17 is installed below groundlevel indicated at 90. The main valve 25 and operating device 30therefor, and the manually operable valve 81, can be installed in avessel or well 91 which is below ground level. The conduit sections 50and 52 can pass between the well' 91 and vessel 17 below ground level. Ahollow duct 92 can be provided between the well 91 and vessel 17 throughwhich the conduit sections 50 and 52 can pass.

In the event the flow control mechanism 18 malfunctions and the liquidin the vessel 17 falls to the level of the outlet 23, and at such timethe discharge conduit 22 is in communication with the branch line 15 ofthe system, air in the vessel can be drawn by suction into the dischargeconduit 22 and flow into the pneumatic liquid disposal system throughthe branch line. When this occurs the partial vacuum developed andmaintainedin the system will be impaired and often can be inadequate topropel waste liquid pneumatically into other branch lines 15 of thesystem from the vessels 17 of other operating units 16 in which suchliquid collects.

In accordance with my invention I provide structure which is independentof the flow control mechanism 18 and operable to prevent air in thevessel 17 from flowing through the outlet 23 thereof due to suction inthe discharge conduit 22 when the control mechanism 18 malfunctions andthe liquid level in the vessel 17 falls to a level at the vicinity ofthe outlet 23. I accomplish this by providing a body 93 in the vessel 17which is capable of floating freely in the body of liquid 24 therein.The floating body 93 in a broad sense serves as a valve member andfunctions independently of the flow control mechanism 18.

When the liquid surface in the vessel 17 falls the floating body 93, dueto the fact that it floats freely in the body of liquid 24, also willfall at the same rate that the liquid surface falls. Since the liquidwithdrawn by suction from the vessel 17 through the discharge conduit 22moves toward the outlet 23, such movement of the liquid induces thefloating body 93 to move toward the discharge conduit 22 and it will benear the outlet 23 as the liquid level approaches the vicinity of theoutlet.

When a partial vacuum prevails in the discharge conduit 22 due to themain valve 25 being open, the floating body 93 will be drawn by suctionagainst the outlet 23 in airtight sealing relation therewith. In thisway the floating body 93 is held fast to the outlet 23 before any air inthe vessel 17 can flow therefrom into the discharge conduit 22 and passinto the branch line of the system.

When the faulty operation of the flow control mechanism 18 has beencorrected and the mechanism functions properly in the manner explainedabove, the main valve 25 will close and suction no longer will betransmitted to the outlet 23. Under these conditions the floating body93 no longer is held fast to the outlet 23 and can move therefrom andmove upward responsive to rise of liquid in the vessel l7.

It will be understood that the floating body 93, which a in thepreferred embodiment shown is spherical, can assume other shapes. In anyparticular case, the shape and specific weight of the floating body aredesirably chosen so that it will always be held fast in sealing relationwith the outlet 23 when the flow control mechanism 18 malfunctions.

In the event the consistency of the body of liquid 24 is such that thefloating body 93, for one reason or another, does not move withcertainty toward the outlet 23 in airtight sealing relation therewith,structure can be employed for guiding the floating body 93 toward theoutlet 23. A tubular member or funnel formed of apertured material, suchas coarse grating or netting, for example, can be employed for suchguiding structure. For example, in FIG. 7 an apertured funnel 94 ismounted by brackets 95 and 96 to the side wall of the vessel 17 forguiding the floating body 93 to the outlet 23; and in FIG. 8 anapertured tubular guide 97 is mounted by brackets98 and 99 to the sidewall of the vessel 17 for guiding the floating body 93 to the outlet 23.When structure is employed for guiding the floating body 93, thefloating body and outlet 23 with which it coacts can assume a variety ofdifferent forms and shapes.

Other ways of guiding the floating body 93 to the outlet 23 areillustrated in FIGS. 9 and 10. In FIG. 9 the floating body 93 is fixedto the outer end of string or light cord 100, the inner end of which isfixed to an eye bolt 101 mounted at the correct height to the side wallof the vessel 17. In FIG. 10 the floating body 93 is fixed to the outerend of a rod 102, the inner end of which is pivotally mounted on abracket 103 at the side wall of the vessel 17.

In the event it is deemed desirable to'employ a floating body that isrelatively light and will displace less liquid and float relatively highat the liquid surface, the main valve 25 can be located at a level belowthe outlet 23 or the discharge conduit 22 can be provided with a pocketdepending downward from the outlet exteriorly of the vessel 17. Underthese conditions liquid always will flow into the discharge conduit 22and be propelled therethrough by vacuum prevailing in the branch line15. In this manner the liquid surface level in the vessel 17 always willfall sufficiently for the floating body 93 to be drawn by suctionagainst the outlet 23 in airtight sealing relation therewith and preventflow of air from the vessel into the discharge conduit 22 when the flowcontrol mechanism malfunctions. In this way the operation of otheroperating units 18 will not be impaired by flow of unwanted air into thesystem which reduces the partial vacuum or negative pressure prevailingin the system and renders the system ineffective to propel waste liquidpneumatically into the branch lines from the vessels of other operatingunits.

I claim:

1. The combination with a pneumatic liquid disposal system which isadapted to be maintained at a partial vacuum, of

a. a vessel adapted to receive liquid, said vessel having an outlet at afirst level,

b. a discharge conduit for connecting the outlet of said vessel to thesystem,

c. valve means in said discharge conduit which is normally closed,

d. control mechanism including first means responsive to the partialvacuum in the system for opening said valve means and second means forrendering said first means operable when the liquid level in said vesselis at a second level which is above the first level, and structure whichis independent of said control mechanism and operable to prevent air insaid vessel from flowing through the outlet thereof when said controlmechanism malfunctions and the outlet is in communication with thesystem and the liquid in said vessel falls to a level at the vicinity ofthe first level. V

2. Apparatus as set forth in claim 1 in which said structure independentof said control mechanism and operable to prevent air in said vesselfrom flowing through the outlet thereof comprises a valve member.

3. Apparatus as set forth in claim 2 in which said valve member isinoperable during normal operation of said control mechanism and becomesoperable to prevent air in said vessel from flowing through the outletthereof responsive only to fall of liquid in said vessel to the level atthe vicinity of the first level.

4. Apparatus as set forth inelaim I in which said structure independentof said control mechanism comprises a body capable of floating in thebody of liquid.

5. Apparatus as set forth in claim 4 in which said body capable offloating functions as a valve member.

6. Apparatus as set forth in claim 5 in which the outlet of said vesselis defined by means which provides a seat for said valve member when theliquid in the vessel falls to the level at the vicinity of the firstlevel.

7. The combination with a pneumatic liquid disposal system which isadapted to be maintained at a partial vacuum, of

a. a plurality of operating units operatively associated with the systemfor collecting waste liquid and for discharging such liquid therefrominto the system,

b. each of said operating units comprising a vessel which has an inletto receive waste liquid and an outlet at a first level,

c.'each of said outlets being connected by a discharge conduit to thesystem,

d. valve means in each of said discharge conduits which is normallyclosed,

e. mechanism for controlling each of said valve means, each controlmechanism including first means responsive to the partial vacuum in thesystem for opening said valve means associated therewith and secondmeans for rendering said first means operable when the liquid level insaid vessel associated therewith is at a second level which is above thefirst level, and

f. a plurality of said operating units each having structure which isindependent of its control mechanism and operable to prevent air in saidvessel in each such unit from flowing through the outlet thereof whensaid control mechanism malfunctions and the outlet is in communicationwith the system and the liquid level in such vessel falls to a level atthe vicinity of the first level, so that flow of air from such vesselinto the system will be prevented and ineffective to adversely impairthe operation of said other units.

8. Apparatus as set forth in claim 7 in which each of said independentstructures operable to prevent air in one of said vessels from flowingthrough its outlet comprises a valve member.

9. Apparatus as set forth in claim 8 in which each of said valve membersis inoperable during normal operation of one of said control mechanismsand becomes operable to prevent air in said vessel from flowing throughits outlet responsive only to fall of liquid in said vessel to the levelat the vicinity of the first level.

10. Apparatus as set forth in claim 7 in which each of said independentstructures comprises a body capable of floating in the body of liquid inone of said vessels.

11. Apparatus as set forth in claim 10 in which each of said floatingbodies functions as a valve member.

12. The combination with a pneumatic liquid disposal system which isadapted to be maintained at a partial vacuum, of

a. a vessel adapted to receive liquid, said vessel having an outlet at afirst level,

b. a discharge conduit for connecting the outlet of said vessel to thesystem,

c. valve means in said discharge conduit which is normally closed,

d. control mechanism including first means responsive to the partialvacuum in the system for opening said valve means and second means forrendering said first means operable when the liquid level in said vesselis at a level which is in a normal range above the first level, and

structure which is independent of said control mechanism and operable toprevent air in said vessel from flowing through the outlet thereof whensaid control mechanism malfunctions and the outlet is in communicationwith the system and the liquid in said vessel falls from the normalrange to a level at the vicinity of the first level.

l3. Apparatus as set forth in claim 12 in which said second means ofsaid control mechanism renders said first means thereof operable to opensaid valve means when the liquid level in said vessel is at the upperend of said normal range and renders said first means inoperable to opensaid valve means when the liquid level in said vessel is at the lowerend of said normal range.

14. Apparatus as set forth in claim 13 in which said structureindependent of said control mechanism comprises a body capable offloating in the body of liquid.

15. The combination with a pneumatic liquid dis posal system which isadapted to be maintained at a partial vacuum, of

a. a plurality of operating units operatively associated with the systemfor collecting waste liquid and for discharging such liquid therefrominto the system,

b. each of said operating units comprising a vessel which has an inletto receive waste liquid and an outlet,

c. each of said outlets being connected by a discharge conduit to thesystem,

d. valve means in each of said discharge conduits for controllingdischarge of waste liquid from said vessels to the system,

e. mechanism for controlling each of said valve means,

f. each of said mechanisms for controlling a different one of said valvemeans being operable responsive to change in the liquid surface level ofthe body of liquid in one of said vessels,

g. a plurality of said vessels each having a body which is capable offloating in the body of liquid therein, and

h. said floating bodies being so constructed and formed that, when theliquid surface level of the body of liquid in which any one of saidbodies is floating falls sufliciently, said floating body will be drawnby suction toward the outlet of said vessel in which said floating bodyis disposed and move into airtight sealing relation therewith, so thatflow of air from such vessel into the system will be prevented and theoperation of said other units will not be impaired.

16. Apparatus as set forth in claim 15 in which said valve means arenormally closed and each of said mechanisms includes first meansresponsive to the partial vacuum in the system for opening a differentone of said valve means and second means for rendering said first meansoperable when the liquid surface level' of the body of liquid in any oneof said vessels is at a given level above its outlet.

17. The combination with a pneumatic liquid disposal system which isadapted to be maintained at a partial vacuum, of

a. a plurality of operating units operatively associated with the systemfor collecting waste liquid and for discharging such liquid therefrominto the system,

b. each of said operating units comprising a vessel which has an inletto receive waste liquid and an outlet,

0. each of said outlets being connected by a discharge conduit to thesystem,

d. valve means in each of said discharge conduits for controllingdischarge of waste liquid from said vessels to the system,

c. mechanism for controlling each of said valve means,

f. each of the mechanisms for a different one of said valve means beingoperable responsive to the partial vacuum in the system,

g. a plurality of said vessels each having a body which is capable offloating in the body of liquid therein, and

h. said floating bodies being so constructed and formed that, when theliquid surface level of the body of liquid in which any one of saidbodies is floating falls sufficiently, said floating body will be drawnby suction toward the outlet of said vessel in which said floating bodyis disposed and move into airtight sealing relation therewith, so thatflow of air from such vessel into the system will be prevented and theoperation of said other units will not be impaired.

i i i l

1. The combination with a pneumatic liquid disposal system which isadapted to be maintained at a partial vacuum, of a. a vessel adapted toreceive liquid, said vessel having an outlet at a first level, b. adischarge conduit for connecting the outlet of said vessel to thesystem, c. valve means in said discharge conduit which is normallyclosed, d. control mechanism including first means responsive to thepartial vacuum in the system for opening said valve means and secondmeans for rendering said first means operable when the liquid level insaid vessel is at a second level which is above the first level, and e.structure which is independent of said control mechanism and operable toprevent air in said vessel from flowing through the outlet thereof whensaid control mechanism malfunctions and the outlet is in communicationwith the system and the liquid in said vessel falls to a level at thevicinity of the first level.
 2. Apparatus as set forth in claim 1 inwhich said structure independent of said control mechanism and operableto prevent air in said vessel from flowing through the outlet thereofcomprises a valve member.
 3. Apparatus as set forth in claim 2 in whichsaid valve member is inoperable during normal operation of said controlmechanism and becomes operable to prevent air in said vessel fromflowing through the outlet thereof responsive only to fall of liquid insaid vessel to the level at the vicinity of the first level. 4.Apparatus as set forth in claim 1 in which said structure independent ofsaid control mechanism comprises a body capable of floating in the bodyof liquid.
 5. Apparatus as set forth in claim 4 in which said bodycapable of floating functions as a valve member.
 6. Apparatus as setforth in claim 5 in which the outlet of said vessel is defined by meanswhich provides a seat for said valve member when the liquid in thevessel falls to the level at the vicinity of the first level.
 7. Thecombination with a pneumatic liquid disposal system which is adapted tobe maintained at a partial vacuum, of a. a plurality of operating unitsoperatively associated with the system for collecting waste liquid andfor discharging such liquid therefrom into the system, b. each of saidoperating units comprising a vessel which has an inlet tO receive wasteliquid and an outlet at a first level, c. each of said outlets beingconnected by a discharge conduit to the system, d. valve means in eachof said discharge conduits which is normally closed, e. mechanism forcontrolling each of said valve means, each control mechanism includingfirst means responsive to the partial vacuum in the system for openingsaid valve means associated therewith and second means for renderingsaid first means operable when the liquid level in said vesselassociated therewith is at a second level which is above the firstlevel, and f. a plurality of said operating units each having structurewhich is independent of its control mechanism and operable to preventair in said vessel in each such unit from flowing through the outletthereof when said control mechanism malfunctions and the outlet is incommunication with the system and the liquid level in such vessel fallsto a level at the vicinity of the first level, so that flow of air fromsuch vessel into the system will be prevented and ineffective toadversely impair the operation of said other units.
 8. Apparatus as setforth in claim 7 in which each of said independent structures operableto prevent air in one of said vessels from flowing through its outletcomprises a valve member.
 9. Apparatus as set forth in claim 8 in whicheach of said valve members is inoperable during normal operation of oneof said control mechanisms and becomes operable to prevent air in saidvessel from flowing through its outlet responsive only to fall of liquidin said vessel to the level at the vicinity of the first level. 10.Apparatus as set forth in claim 7 in which each of said independentstructures comprises a body capable of floating in the body of liquid inone of said vessels.
 11. Apparatus as set forth in claim 10 in whicheach of said floating bodies functions as a valve member.
 12. Thecombination with a pneumatic liquid disposal system which is adapted tobe maintained at a partial vacuum, of a. a vessel adapted to receiveliquid, said vessel having an outlet at a first level, b. a dischargeconduit for connecting the outlet of said vessel to the system, c. valvemeans in said discharge conduit which is normally closed, d. controlmechanism including first means responsive to the partial vacuum in thesystem for opening said valve means and second means for rendering saidfirst means operable when the liquid level in said vessel is at a levelwhich is in a normal range above the first level, and e. structure whichis independent of said control mechanism and operable to prevent air insaid vessel from flowing through the outlet thereof when said controlmechanism malfunctions and the outlet is in communication with thesystem and the liquid in said vessel falls from the normal range to alevel at the vicinity of the first level.
 13. Apparatus as set forth inclaim 12 in which said second means of said control mechanism renderssaid first means thereof operable to open said valve means when theliquid level in said vessel is at the upper end of said normal range andrenders said first means inoperable to open said valve means when theliquid level in said vessel is at the lower end of said normal range.14. Apparatus as set forth in claim 13 in which said structureindependent of said control mechanism comprises a body capable offloating in the body of liquid.
 15. The combination with a pneumaticliquid disposal system which is adapted to be maintained at a partialvacuum, of a. a plurality of operating units operatively associated withthe system for collecting waste liquid and for discharging such liquidtherefrom into the system, b. each of said operating units comprising avessel which has an inlet to receive waste liquid and an outlet, c. eachof said outlets being connected by a discharge conduit to the system, d.valve means in each of said discharge conduits for controlling dischargeof waste liQuid from said vessels to the system, e. mechanism forcontrolling each of said valve means, f. each of said mechanisms forcontrolling a different one of said valve means being operableresponsive to change in the liquid surface level of the body of liquidin one of said vessels, g. a plurality of said vessels each having abody which is capable of floating in the body of liquid therein, and h.said floating bodies being so constructed and formed that, when theliquid surface level of the body of liquid in which any one of saidbodies is floating falls sufficiently, said floating body will be drawnby suction toward the outlet of said vessel in which said floating bodyis disposed and move into airtight sealing relation therewith, so thatflow of air from such vessel into the system will be prevented and theoperation of said other units will not be impaired.
 16. Apparatus as setforth in claim 15 in which said valve means are normally closed and eachof said mechanisms includes first means responsive to the partial vacuumin the system for opening a different one of said valve means and secondmeans for rendering said first means operable when the liquid surfacelevel of the body of liquid in any one of said vessels is at a givenlevel above its outlet.
 17. The combination with a pneumatic liquiddisposal system which is adapted to be maintained at a partial vacuum,of a. a plurality of operating units operatively associated with thesystem for collecting waste liquid and for discharging such liquidtherefrom into the system, b. each of said operating units comprising avessel which has an inlet to receive waste liquid and an outlet, c. eachof said outlets being connected by a discharge conduit to the system, d.valve means in each of said discharge conduits for controlling dischargeof waste liquid from said vessels to the system, e. mechanism forcontrolling each of said valve means, f. each of the mechanisms for adifferent one of said valve means being operable responsive to thepartial vacuum in the system, g. a plurality of said vessels each havinga body which is capable of floating in the body of liquid therein, andh. said floating bodies being so constructed and formed that, when theliquid surface level of the body of liquid in which any one of saidbodies is floating falls sufficiently, said floating body will be drawnby suction toward the outlet of said vessel in which said floating bodyis disposed and move into airtight sealing relation therewith, so thatflow of air from such vessel into the system will be prevented and theoperation of said other units will not be impaired.